EGGS HARVEST RECORDS VERSUS NIGHT COUNTS IN Caiman latirostris, WHAT DO THEY REALLY MEAN?

LARRIERA, A., A. IMHOF, P. SIROSKI AND C. I. PIÑA

Santa Cruz, Bolivia

Congreso; XIX Working Meeting of the Crocodile Specialist Group (CSG/SSC/UICN); 2008

Crocodile Specialist Group

To obtain information on the situation of a crocodilian population under a management technique such as ranching,  is crucial in order to verify the sustainability of the program   But it seems very difficult to achieve with the standard night counts monitoring techniques in some species with cryptic behavior like Caiman latirostris on the other. We are presenting and discussing, the value of the information during 15 years of eggs harvests in one of the most studied populations of the species. In a location where the effort of the harvest  was similar every year since the beginning of the project, and where the majority of the nests (90 to 95%) were always available for the harvest.   We compared these with our monitoring records in the same period and location. Nevertheless,  we found that that the night counts showed an average recovery of the population of 50%, the number of nests and eggs harvested increased up to  750%. On the other hand, we found that negative environmental conditions like droughts, affected positively the results of the   night counts, with more animals counted per km. (9.2), but clearly, those years the eggs harvest was lower than the ones with average environmental conditions, which produces 5 or 6 times more eggs, when at the same time night counts were of 5 to 6 animals per km. Finally, we also found that the most important increase in eggs harvest happened after the nine year from the first releasing, which coincide with the published information on the age of sexual maturity of the species. We are proposing here to utilize the information on eggs harvest combined with the night counts results, in order to be able to evaluate the population situation of species with such habitat preferences as C. latirostris.